A new technique of two dimensional electrophoresis to examine, distinguish and quantify cell surface membrane proteins and glycoproteins was developed and applied to HL-60 and K562 cell differentiation. The technique may be useful in the study of cellular drug resistance. K562 cells were induced to differentiate by hemin and studied for comparative morphology, cytochemistry, and cytogenetics. The data indicate the existance of clonal evolution in the K562 line. The synergetic interaction of cytosine arabinoside and deoxyguanosine were studied in HL60 and K562 cells.